Lens



July 20 1926.

I E. D. TILLYER LENS Original Fi August 7, 1924 CENTER OF ROTATION 0FEYE BALL 533,6. 3 t Edgar D. linger.

Patented July 20, 1926.

UNITED STATES PATENT OFFICE.

EDGAR D. TILLYER, OF SOUTHBRIDGE, MASSACHUSETTS, ASSIGNOR TO AMERICAN P-TICAL COMPANY, OF SOUTHBRIDGE, MASSACHUSETTS, A VOLUNTARY ASSOCIA- TIONOF MASSACHUSETTS.

LENS.

Original application filed August 7, 1924, Serial No. 730,565.

November 21, 1925.

The present invention relates to a new and useful process for makingophthalmic multifocal lenses which are well known in the art as fused orKryptok lenses. It is a well known fact that in a finishedlens of thistype the oblique vision through the reading portion is variable,increasing in power from the center towards the margin, which is quite apronounced and objectionable aber l ration. I

This application is a division of my application Serial No.'730,565filed August 7, 1924.

An important object of the invention is to provide an improvedmultifocal lens formed of two pieces of glass of dilferent indexes ofrefraction which will be practically free from the objectionablevariations present in the reading portion of the prior art lenses ofthis type.

Another very important object of the invention is to provide a new andimproved process for forming two part lenses whereb the objectionableobli ue errors will be e iminated so as to pro uce a reasonably correctvision or visions through the reading portion of the lens.

Another very im ortant object of the in-" vention is to provi e amultifocal lens and rocess for forming the same wherein the iinishedlens will have a substantially elliptical shaped button and in which thebutton will be composed of two major meridians, the

curvatures ofwhich will be different to comas pensate for the obliqueerrors.

Other advantages and objects of the invention will become ap arentduring the course of the following escription.

In the drawings, wherein like numerals a0 are employed to designate likeparts throughout the same Figure 1 is a top plan view of a lens blanksimilar to the prior art structures.

Figure 2 is a section taken on line 22 in 4a Fi ure 1.

igure 3 is a perspective view showing a blank as illustrated in Figure 1after the first step of my improved process.

Figure 4 is a top plan view of a blank afoo ter it has been formed inaccordance with thepresent invention.

Divided and this application filed Serial No. 70,563.

Figure 5 is a section taken on line 55 of Figure 4. v

Figure 6 is a section taken on line 6-6 in Figure 4.-

Figure 7 is a diagrammatic view of a cross section of a bifocal lensshowing oblique vision through the reading portion.

It will. be noted from the diagrammatic view, Figure 7, that the readingportion or segment of a bifocal lens being placed at the bottom of thelens below the center of the eye and below the optical axis of thedistance portion, practically all the rays of light from the center ofthe eye will pass obliquely through the reading portion. In other words,a bifocal lens located in its position of greatest use before the eye ispractically alwa s looked thru in an oblique direction, an it is wellknown that oblique vision is not as clear as vision along the opticalaxis or vision that goes normally thru the lens. For this reason, amongothers, it has been found that there is considerabl variation in thepower at the center of the segment or reading portion of a fused bifocalfrom that 0 the marginal portions, as much as half diopter variationbeing noted in some of the ordinary numbers of these lenses. Therefore,one of the main objects of this invention is to neutralize thisvariation of power in the various portions of the reading portion of thebifocal. It will be ob vious that, as shown, the greater error willprobably fall in the vertical plane when the lens is in position beforethe eye, but there may be variations in the horizontal or other planesand it is a part of the conception of this invention that thesevariations in the horizontal, vertical or any other plane may be made bproviding the necessary means for neutra 1zing the error at any givenangle or angles.

In the drawings wherein for the purpose of illustration is shown apreferred embodiment of the invention, the numeral 10 designates amultifocal lens blank which is provided with the insert or button 11.

Heretofore, the recesses in which the bution 11 is fused have beenspherical in curvature. The spherical recesses have been ob iectionabledue to the fact that the vision thru the button increased in power fromthe centre toward the edge thereof so that the true vision has not beenobtained when lookhag through the button near the marginal e ge.

In accordance with the present invention, the recess having a s hericalcurve is formed in the blank and the utton 11 is fused therein. Afterthis operation, the blank as illustrated in Figures 1 and 2, is placedupon the block 12 which has a toric surface formed thereon, i. e., asurface having diflerent curvatures in the two major meridians. In otherwords, the major meridiansof the block 12 which are at right angles toeach other have different curvatures. The blank is then placed on theblock 12 and suflicient heat is applied to the parts to permit the lensblank to settle down so as to assume the surface shape 13 of the block12. As is'shown in Figure 3, the button 11 will assume an ellipticalshape as is shown in Fig. 4.

The action of the lens blank upon the block is clearly shown in Figures5 and 6, in-that it is shown with a toric button which is really formedbecause of the fact that the glass is so bent over the block under theaction of heat that the button is bent or distorted into an ellipticalshape having a minor and a major meridian of' different curvatures. Itwill be seen from the foregoing that the spherical countersink has beenbent to a toric surface shape.

A slight modification includes heating the button and blank together tofuse the button into the recess, after which the heat is in creased soas to let the blankdrop to a toric shape, thus bending thebutton as inthe first instance, but in one continuous operation.

It is to be understood that the button will not necessarily have toassume the elliptical shape positioned as shown in Figure 4 be cause themeridians can be shifted to any required angular position to neutralizethe oblique errors to desired requirements.

It will, therefore, be seen from the foregoing that I have provided alens and process for forming the same whereby the amount of obliqueerrors present in the button or reading (portion has been reduced to aminimum, an neutralized as desired.

It is to be understood that the form of the invention herewith shown anddescribed is to be taken as the preferred embodiment of the same andthat various changes in the size, shape and arrangement of parts may beresorted to without departing from the spirit of the invention or thescope of the subjoined claims.

Having thus described my invention, I claim 1. The process of producinga multifocal lens consisting in fusing a spherical se ment in a majorblank and then displacingt e entire blank to bend the segment into toricform.

2. The process of producing a multifocal lens consisting in fusing aspherical segment in a major blank and then displacing the entire blankby the application of heat to bend the segment into toric form.

3. The process of producing a multifocal lens consisting in fusing asegment in a major blank placing the blank on a tone block, thenapplying heat to bend the blank down on the toric block to change thesegment into toric form. s

4. The process of producing multifocal lenses consisting of fusing aspherical segment in a major blank, placing the blank on a toric block,applying heat to the blank till the same will drop down on the block andbend the segment into toric form, and change the shape of the segmentfrom circular to elliptical shape.

EDGAR D. TILLYER.

